Gelatin Encapsulated Microtubules (GEM) adhere to tumor vessel walls for periods of time up to 10 minutes. Because bubbles are highly echogenic to ultrasound, they act as ultrasonic reflectors and identify the vasculature of tumors. Normal vessels clear bubbles quickly. Thus this time lag between the two permits separation and localization of tumors. Because bubbles are so echogenic, it is hoped that they can be used to identify small tumors. Phase I program developed a 3 micron GEM microparticle capable of clearing the lungs to enter the systemic circulation. In order to increase the number of particles entering a general area, magnetite, magnetic iron oxide, has been added to the inner wall. Thus the clinician can steer particles entering a general area and increase the local population and echogenicity. The primary goal of Phase II studies is to demonstrate efficacy of the concept in vivo. The agent will be tested on tumor models and on spontaneous tumors in dogs and cats. Following optimization of particles methodology will be developed to assess various types of cancer using a mouse model. The intent of the technology is to detect small tumors when the possibility of cure is greatest.